No description available.

Up to 87% of the world’s wetlands have been destroyed, considerably reducing ecosystem services these wetlands once provided. More recently, many wetlands are being restored in an attempt to regain their ecosystem service. This study seeks to determine the effects of restored wetlands on local bat habitat use. Bat activity was found to be significantly higher around the wetlands when compared to distant grassy fields; however, no significant difference was found among the restored wetlands and a remote cattle farm containing multiple water features. Geospatial models of bat distribution and bat foraging were produced using machine learning that showed higher habitat suitability and foraging activity around restored wetlands than around distant grassy fields, suggesting that wetlands provide vital habitat for insectivorous bats. This study demonstrates that restored wetlands promote bat activity and bat foraging, and restoring wetlands may be a useful means of increasing natural pest control over nearby farmlands.

1 Assesment of land use influence on landscape naturalness Abstract Human activities are putting an increasing pressure on natural areas. Complex understanding and evaluation of human impact on the environment is considered to be a key tool to preserve natural balance. Biodiversity was chosen as proxy for naturalness as it has been recognized as one of the main components of environmental stability. Several different indices has been developed to assess human-induced changes in biodiversity. In this study, mean abundance of original species relative to their abundance in undisturbed ecosystems (MSA) is used as an indicator for current state of naturalness. Indicator MSA is built on simple cause-effect relationships between environmental drivers and biodiversity impacts, based on state-of-the-art knowledge. Drivers considered are landcover change, land-use intensity, fragmentation and infrastructure development. As most of biodiversity indices, MSA illustrate prevailingly poor condition of nature as a result of human induced pressures, especially land cover change. Considering constantly increasing population and economic development human pressure grow is likely to continue during the coming decades with irreversible loss in the diversity of life on the Earth. Keywords: Mean species abundance (MSA) - land...

Changes in species abundance and richness, stand structure, and species responses to habitat characteristics including disturbance intensity, were investigated in 28 permanent sample plots (PSP) covering a total area of about 6.2 hectares of subtropical rainforests in north-east New South Wales, Australia. The disturbance that occurred over 36 years previously varied from unlogged (controls), through single-tree selection (light), moderate selection and repeated single-tree selection to intensive (heavy) logging. Multivariate and univariate approaches were used to investigate changes in various plant groups, including all vascular plants, regenerating species (trees and understorey species > 1.3 m in height and < 10 cm diameter at 1.3 m above the ground level (dbh)), juvenile trees (regenerating species capable of attaining at least 10 cm dbh), and trees ¡Ý 10 cm dbh. In addition, dynamic parameters (recruitment, growth and mortality) were estimated using hierarchical multilevel modelling and parameter estimates used to simulate behaviour of the subtropical rainforest tree species in unlogged and logged stands, both within and beyond the range of available data.Chronological post-disturbance responses and changes in species abundance and richness as well as stand structure for trees ¡Ý 10 cm dbh were investigated using 20 PSP in a bid to better understand rainforest post-disturbance regeneration. The results portrayed minor and gradual ecological changes in the undisturbed controls analogous with natural forest dynamics where the changes were not significant. In logged sites, initial gradual changes were followed with more rapid and significant changes.In both unlogged and logged stands, the changes proceeded through three clearly identifiable stages. The first two stages lasted between 5 and 15 years each. In the initial stage, the number of individuals decreased in species with high frequency mainly in the shade tolerant species, with little or no change in species richness. In the second stage, species abundance and richness changed due to localised species turnover, replacement and losses with very little recruitment, and the numbers of both speciesand individuals declined to minima. In the third stage, due to recruitment beyond the 10 cm dbh, the net loss of species and trees ¡Ý 10 cm dbh were halted and reversed, and species diversity and abundance began to return to pre-disturbance levels.Species abundance and diversity for both shade tolerant and intolerant species in less intensively logged sites (single-tree selection logging) have recovered to levels comparable with that observed in the controls, but more intensively logged sites have not recovered to similar levels. Increased logging intensity was associated with increased and decreased densities in the shade intolerant and ¨Ctolerant species respectively. It was evident that stand structure in logged sites had yet to recover to levels comparable with that of unlogged controls. It appears the restoration of floristic diversity to levels similar to that of intact primary forest takes considerably less time than structural recovery. Changes in regeneration patterns in a subtropical rainforest in north-east New South Wales were investigated for a 13-year period during the 3rd and 4th decades following repeated single-tree selection logging. Multivariate and univariate analyses results showed that there were no significant differences in floristic assemblages within and between censuses; however, two contrasting trends of changes in plant groups were detected. In trees ¡Ý 10 cm dbh, the stem density and species richness increased in shade tolerant group, and while stem density increased in the shade intolerant group, species richness decreased during the study period. Amongst smaller sized species including trees (< 10 cm dbh), a general decrease in species richness was observed along with significant changes in stem densities (P = 0.03) with the number of individuals in the shade tolerant species increasing, while that of both shade intolerant and vine species decreased. Excluding the vines and understorey species from the broader regenerating species group, revealed a decrease in species richness in juvenile canopy tree, and a significant change in densities (P = 0.004) with the number of individuals in shade tolerant increasing, while that of shade intolerant trees decreased. A comparison between the canopy trees ¡Ý 10 cm dbh and juvenile canopy trees group showed that these groups were tending towards similar floristic assemblages. These results suggest gradual replacement of shade intolerant by shade tolerant species as stands were tending toward later stages of recovery within the regeneration. The results also show that the inclusion of regenerating species in long-term studies is both complementary to the larger plant component and more revealing of both trends and changes.Species-specific estimates of shade tolerance and size structure at maturity derived from observations on 23 plots were used to intuitively group 277 vascular plant species into 3 main groups including full floristic (all together), shade tolerant and intolerant groups. The shade tolerant and intolerant groups were further grouped into smaller plants groups depending on the development stage and maximum size at maturity. These groups included regenerating species, juvenile trees, and trees ¡Ý 10 cm dbh. Multivariate analyses of these nominated groups revealed that floristic assemblages were significantly associated with environmental gradients based on simple site characteristics.At the landscape (larger) scale, the floristic assemblages were significantly different between low (200-400), mid (400-700) and high altitude (over 700 meters above sea level). In addition, abundance of shade tolerant species including Doryphora sassafras Endl, Orites excelsa R.Br and Caldcluvia paniculosa (F.Muell) Hoogland was positively correlated with the altitudinal gradient. At the smaller (local) scale, intensively logged sites where large gaps were created had recovered their species richness, but effects of past logging were evident in trees ¡Ý 10 cm dbh, especially trees greater than 50 cm dbh where species abundance in shade tolerant decreased significantly. Less intensively logged sites at mid altitude where a few stems were removed had recovered their species richness in respect to trees ¡Ý 10 cm dbh, but the small gaps created may have healed quickly for appreciable regeneration response to occur, as juvenile trees component was significantly different to that of the (unlogged) controls.The abundance of shade intolerant and juvenile shade tolerant tree species increased in concert with levels of disturbance and abundance of shade intolerant species such as Duboisia myoporoides R.Br, Acacia melanoxylon R.Br, Rubus moorei F.Muell and R. hilli F.Muell was positively correlated with the disturbance gradient. Increase in number of individuals of certain tree species was positively correlated with both disturbance intensity and topography (mid slope through lower slope to creek/gully), but negatively correlated with aspect (NE - NW). We concluded that logged sites are yet to recover their pre-logging stand structure and rainforest tree species were found in sites where favourable recruitment and growth conditions were the encountered. These results show that logged sites had not yet regenerated to the pre-logging stand structure. They also show that habitat characteristics including history of disturbance and topography can influence the floristic assemblages in the sub-tropical rainforests at both the small (local) and large (geographic) scales. This supports the environmental control model that states ¡°species are found at sites where they encounter favourable living conditions¡±. Site characteristics as surrogate for some of these favourable living conditions were identified as useful potential variables to investigate the rainforest dynamic parameters (growth, recruitment and mortality) in both logged and unlogged stands.A quantitative model was developed using over 3 decades of data to describe and simulate the dynamics including recruitment, growth and mortality in unlogged stands and others subjected to different silvicultural regimes in uneven-aged mixed-species subtropical rainforests of north-eastern New South Wales. Hierarchical multilevel regression analyses including Poisson, Binomial and multinomial logit regression were used to estimate the rainforest dynamic parameters based on the assumption that trees perform differently in space and time, thus there are variations at both the plot and tree by measurement levels.Variations at the tree level required the botanical identity of trees to species level, and then the species-specific size at maturity and shade tolerance were used to classify species into 5 groups, each consisting of species with similar ecological characteristics. These groups were labelled as emergent and shade tolerant main canopy, shade tolerant mid canopy, shade tolerant understoreys, moderate shade tolerant and persistent, and shade intolerant pioneer tree species. Significant variables at the plot level including site characteristics such as topography (elevation, slope and aspect), and past disturbance were used as explanatory variables in species group models. The final model is as a classical matrix management-oriented model with an ecological touch and maximum size-dependent parameters of ingrowth and outgrowth. The model provides a tool to simulate stand performance after logging and to assess silvicultural prescriptions before they are applied in these types of forests.The simulations indicate that full recovery following a logging intensity where 47% of the overstorey basal area is removed with a checkerboard of logged and unlogged patches (group selection) on a 120-year cycle could enable sustainable timber production without compromising the ecological integrity in these forests. Following single-tree selection (33%), recovery takes about 150 years, and more intensive harvesting practices where 50-78% overstorey basal area is removed may take 180-220 years to recover. Pre-harvest climber cutting coupled with poisoning of non-timber species followed by intensive logging of merchantable trees would allow logging on a 300-year cycle. Shorter logging cycles may lead to changes in the forest structure and floristic composition where the overall species density is low with higher density of shade intolerant species.

No description available.

Changes in species abundance and richness, stand structure, and species responses to habitat characteristics including disturbance intensity, were investigated in 28 permanent sample plots (PSP) covering a total area of about 6.2 hectares of subtropical rainforests in north-east New South Wales, Australia. The disturbance that occurred over 36 years previously varied from unlogged (controls), through single-tree selection (light), moderate selection and repeated single-tree selection to intensive (heavy) logging. Multivariate and univariate approaches were used to investigate changes in various plant groups, including all vascular plants, regenerating species (trees and understorey species > 1.3 m in height and < 10 cm diameter at 1.3 m above the ground level (dbh)), juvenile trees (regenerating species capable of attaining at least 10 cm dbh), and trees ¡Ý 10 cm dbh. In addition, dynamic parameters (recruitment, growth and mortality) were estimated using hierarchical multilevel modelling and parameter estimates used to simulate behaviour of the subtropical rainforest tree species in unlogged and logged stands, both within and beyond the range of available data.Chronological post-disturbance responses and changes in species abundance and richness as well as stand structure for trees ¡Ý 10 cm dbh were investigated using 20 PSP in a bid to better understand rainforest post-disturbance regeneration. The results portrayed minor and gradual ecological changes in the undisturbed controls analogous with natural forest dynamics where the changes were not significant. In logged sites, initial gradual changes were followed with more rapid and significant changes.In both unlogged and logged stands, the changes proceeded through three clearly identifiable stages. The first two stages lasted between 5 and 15 years each. In the initial stage, the number of individuals decreased in species with high frequency mainly in the shade tolerant species, with little or no change in species richness. In the second stage, species abundance and richness changed due to localised species turnover, replacement and losses with very little recruitment, and the numbers of both speciesand individuals declined to minima. In the third stage, due to recruitment beyond the 10 cm dbh, the net loss of species and trees ¡Ý 10 cm dbh were halted and reversed, and species diversity and abundance began to return to pre-disturbance levels.Species abundance and diversity for both shade tolerant and intolerant species in less intensively logged sites (single-tree selection logging) have recovered to levels comparable with that observed in the controls, but more intensively logged sites have not recovered to similar levels. Increased logging intensity was associated with increased and decreased densities in the shade intolerant and ¨Ctolerant species respectively. It was evident that stand structure in logged sites had yet to recover to levels comparable with that of unlogged controls. It appears the restoration of floristic diversity to levels similar to that of intact primary forest takes considerably less time than structural recovery. Changes in regeneration patterns in a subtropical rainforest in north-east New South Wales were investigated for a 13-year period during the 3rd and 4th decades following repeated single-tree selection logging. Multivariate and univariate analyses results showed that there were no significant differences in floristic assemblages within and between censuses; however, two contrasting trends of changes in plant groups were detected. In trees ¡Ý 10 cm dbh, the stem density and species richness increased in shade tolerant group, and while stem density increased in the shade intolerant group, species richness decreased during the study period. Amongst smaller sized species including trees (< 10 cm dbh), a general decrease in species richness was observed along with significant changes in stem densities (P = 0.03) with the number of individuals in the shade tolerant species increasing, while that of both shade intolerant and vine species decreased. Excluding the vines and understorey species from the broader regenerating species group, revealed a decrease in species richness in juvenile canopy tree, and a significant change in densities (P = 0.004) with the number of individuals in shade tolerant increasing, while that of shade intolerant trees decreased. A comparison between the canopy trees ¡Ý 10 cm dbh and juvenile canopy trees group showed that these groups were tending towards similar floristic assemblages. These results suggest gradual replacement of shade intolerant by shade tolerant species as stands were tending toward later stages of recovery within the regeneration. The results also show that the inclusion of regenerating species in long-term studies is both complementary to the larger plant component and more revealing of both trends and changes.Species-specific estimates of shade tolerance and size structure at maturity derived from observations on 23 plots were used to intuitively group 277 vascular plant species into 3 main groups including full floristic (all together), shade tolerant and intolerant groups. The shade tolerant and intolerant groups were further grouped into smaller plants groups depending on the development stage and maximum size at maturity. These groups included regenerating species, juvenile trees, and trees ¡Ý 10 cm dbh. Multivariate analyses of these nominated groups revealed that floristic assemblages were significantly associated with environmental gradients based on simple site characteristics.At the landscape (larger) scale, the floristic assemblages were significantly different between low (200-400), mid (400-700) and high altitude (over 700 meters above sea level). In addition, abundance of shade tolerant species including Doryphora sassafras Endl, Orites excelsa R.Br and Caldcluvia paniculosa (F.Muell) Hoogland was positively correlated with the altitudinal gradient. At the smaller (local) scale, intensively logged sites where large gaps were created had recovered their species richness, but effects of past logging were evident in trees ¡Ý 10 cm dbh, especially trees greater than 50 cm dbh where species abundance in shade tolerant decreased significantly. Less intensively logged sites at mid altitude where a few stems were removed had recovered their species richness in respect to trees ¡Ý 10 cm dbh, but the small gaps created may have healed quickly for appreciable regeneration response to occur, as juvenile trees component was significantly different to that of the (unlogged) controls.The abundance of shade intolerant and juvenile shade tolerant tree species increased in concert with levels of disturbance and abundance of shade intolerant species such as Duboisia myoporoides R.Br, Acacia melanoxylon R.Br, Rubus moorei F.Muell and R. hilli F.Muell was positively correlated with the disturbance gradient. Increase in number of individuals of certain tree species was positively correlated with both disturbance intensity and topography (mid slope through lower slope to creek/gully), but negatively correlated with aspect (NE - NW). We concluded that logged sites are yet to recover their pre-logging stand structure and rainforest tree species were found in sites where favourable recruitment and growth conditions were the encountered. These results show that logged sites had not yet regenerated to the pre-logging stand structure. They also show that habitat characteristics including history of disturbance and topography can influence the floristic assemblages in the sub-tropical rainforests at both the small (local) and large (geographic) scales. This supports the environmental control model that states ¡°species are found at sites where they encounter favourable living conditions¡±. Site characteristics as surrogate for some of these favourable living conditions were identified as useful potential variables to investigate the rainforest dynamic parameters (growth, recruitment and mortality) in both logged and unlogged stands.A quantitative model was developed using over 3 decades of data to describe and simulate the dynamics including recruitment, growth and mortality in unlogged stands and others subjected to different silvicultural regimes in uneven-aged mixed-species subtropical rainforests of north-eastern New South Wales. Hierarchical multilevel regression analyses including Poisson, Binomial and multinomial logit regression were used to estimate the rainforest dynamic parameters based on the assumption that trees perform differently in space and time, thus there are variations at both the plot and tree by measurement levels.Variations at the tree level required the botanical identity of trees to species level, and then the species-specific size at maturity and shade tolerance were used to classify species into 5 groups, each consisting of species with similar ecological characteristics. These groups were labelled as emergent and shade tolerant main canopy, shade tolerant mid canopy, shade tolerant understoreys, moderate shade tolerant and persistent, and shade intolerant pioneer tree species. Significant variables at the plot level including site characteristics such as topography (elevation, slope and aspect), and past disturbance were used as explanatory variables in species group models. The final model is as a classical matrix management-oriented model with an ecological touch and maximum size-dependent parameters of ingrowth and outgrowth. The model provides a tool to simulate stand performance after logging and to assess silvicultural prescriptions before they are applied in these types of forests.The simulations indicate that full recovery following a logging intensity where 47% of the overstorey basal area is removed with a checkerboard of logged and unlogged patches (group selection) on a 120-year cycle could enable sustainable timber production without compromising the ecological integrity in these forests. Following single-tree selection (33%), recovery takes about 150 years, and more intensive harvesting practices where 50-78% overstorey basal area is removed may take 180-220 years to recover. Pre-harvest climber cutting coupled with poisoning of non-timber species followed by intensive logging of merchantable trees would allow logging on a 300-year cycle. Shorter logging cycles may lead to changes in the forest structure and floristic composition where the overall species density is low with higher density of shade intolerant species.

The objectives of this study were: 1) to compare and contrast the effects of variations in natural densities of two common freshwater predators of crustacean zooplankton, Chaoborus spp. and Mysis relicta; and 2) to determine whether the combined impacts of these predators together differed from their effects when alone. In deep (>10m) mesocosms, additions of Chaoborus and Mysis at natural densities did not result in large changes in zooplankton abundances, lengths, or biomass. Significant decreases in abundance were observed only for Bosmina longirostris and Daphnia spp. In small (~20L) enclosures, higher predator densities caused zooplankton declines over three days. Strong interactive effects between Chaoborus and Mysis were not detected in either the large or small enclosures. This suggests that the combined effects of these two predators can be predicted from their effects determined in isolation.

The objectives of this study were: 1) to compare and contrast the effects of variations in natural densities of two common freshwater predators of crustacean zooplankton, Chaoborus spp. and Mysis relicta; and 2) to determine whether the combined impacts of these predators together differed from their effects when alone. In deep (>10m) mesocosms, additions of Chaoborus and Mysis at natural densities did not result in large changes in zooplankton abundances, lengths, or biomass. Significant decreases in abundance were observed only for Bosmina longirostris and Daphnia spp. In small (~20L) enclosures, higher predator densities caused zooplankton declines over three days. Strong interactive effects between Chaoborus and Mysis were not detected in either the large or small enclosures. This suggests that the combined effects of these two predators can be predicted from their effects determined in isolation.

Orientador: Marlies Sazima / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T01:09:15Z (GMT). No. of bitstreams: 1 Bugoni_Jeferson_M.pdf: 1779584 bytes, checksum: 28e75bbf88520708b08ce2dffeb7b431 (MD5) Previous issue date: 2013 / Resumo: Neutralidade, complementaridade nos fenótipos das espécies e restrições filogenéticas são alguns dos principais determinantes da estrutura das redes de interações entre espécies. Embora diversos padrões estruturais das redes tenham sido descritos, a importância relativa dos mecanismos que os geram permanece em discussão. Neste estudo, investigamos a importância relativa da abundância (neutralidade) e da complementaridade fenológica e morfológica (interações permitidas ou proibidas) na estruturação de uma rede de interações planta-beija-flor na Floresta Atlântica (SE Brasil). Encontramos que fenologia e morfologia juntas compõem o modelo que melhor prediz a frequência de interações entre pares de espécies, entretanto os modelos não foram capazes de predizer acuradamente a maioria das métricas agregadoras de redes (aninhamento, conectância, equitabilidade e assimetria na força de interação). Em contraste com os estudos prévios, nossos resultados mostram que a importância das interações proibidas pode sobrepujar a importância da abundância na determinação de quais interações ocorrem na comunidade. Os estudos prévios podem ter subestimado a importância das interações proibidas em detrimento das abundâncias relativas (neutralidade) devido à insuficiência amostral. Adicionalmente, discutimos que as métricas de redes, ainda que sejam úteis para descrever padrões de interações em comunidades, podem ser pouco informativas sobre os mecanismos geradores da estrutura das redes de interações / Abstract: Neutrality and complementarity in the phenotypes of species as well as phylogenetic constraints are the main determinants of the structure of interaction networks. Although several structural patterns of the networks have been described, the relative importance of the mechanisms that generate them remains under discussion. In this study, we investigated the relative importance of abundance (neutrality) and phenological and morphological complementarity (forbidden links) in the structure of a plant-hummingbird network in the Atlantic Forest (SE Brazil). We found that the combination of phenological and morphological matches of interacting species represents the best model that predicts the frequency of interactions between pairs of species. Nevertheless, models were not able to accurately predict most of the network metrics - nestedness, connectance, and interaction evenness and interaction asymmetry. In contrast to previous studies, our results highlight the importance of forbidden links that may overcome the importance of relative abundances (neutrality) in the structure of the interactions at the community level. Previous studies could have underestimated the importance of complementarity in the species phenotypes due to insufficient sampling effort, while neutrality was likely overestimated. Finally, although network metrics have been useful for describing network structures, we argue that these metrics can tell us little about the mechanisms that generate the structure of networks / Mestrado / Ecologia / Mestre em Ecologia

As distribuições de abundância das espécies (SADs) são consideradas uma maneira informativa e sintética de descrever a diversidade biológica, e revelam um dos padrões mais bem estabelecidos da ecologia, que é a predominância de espécies raras nas comunidades biológicas. A generalidade deste padrão o torna relevante para a análise de outros parâmetros das comunidades. Além disso, ele levou ao desenvolvimento dos modelos teóricos de SAD. Os modelos estatísticos de SAD, por sua vez, passaram a ocupar um papel central na biologia, como principio empírico que sustenta várias teorias ecológicas. Preston sugeriu em 1948 que as SADs das comunidades naturais teriam uma distribuição aproximadamente Lognormal, porém apareciam truncadas devido ao efeito do tamanho amostral, cuja forma real só seria revelada, portanto, em amostras grandes. Esta ideia vai de encontro à propriedade estatística da consistência, que implica que o acúmulo de evidência causado pelo aumento do tamanho amostral favorece a aproximação ao modelo verdadeiro, bem como às estimativas de seus parâmetros. Além do efeito do tamanho amostral, os padrões de distribuição de abundância podem diferir dependendo da medida de abundância utilizada. Estudos sugerem que a biomassa seria uma medida de abundância mais adequada para revelar a distribuição subjacente de uma comunidade biológica em amostras ou escalas menores (differential veiling). Neste contexto, nosso objetivo principal neste trabalho foi investigar e discutir a vantagem de considerarmos a biomassa como medida de abundância nos modelos teóricos de distribuição de abundância das espécies. Avaliamos, então, o efeito do tamanho da amostra sobre a qualidade dos ajustes dos modelos sob duas diferentes medidas de abundância: biomassa e número de indivíduos. Simulamos amostras de diferentes tamanhos a partir de amostragens aleatórias de uma base de dados empírica e as ajustamos a diferentes modelos de SADs . Com isso, pudemos avaliar a eficiência das amostras - com cada medida de abundância - em revelar o modelo correto, bem como a acurácia e precisão das estimativas dos parâmetros desses modelos. Para o presente estudo, utilizamos um grupo com reconhecido potencial indicador e relevância para estudos ecológicos, os besouros Scarabaeinae. Os resultados encontrados neste estudo mostram que a maior eficiência da biomassa para revelar a distribuição subjacente não é tão geral quanto sugerem os trabalhos anteriores Os critérios de análise utilizados não favoreceram consistentemente a biomassa como medida mais eficiente em revelar o modelo correto e apresentar maior acurácia e precisão nas estimativas de seus parâmetros. Assim, a afirmativa de que a SAD de biomassa não é oculta (veiled) em escalas e amostra menores não parece ser geral. Os resultados obtidos no presente estudo também indicam que o padrão de differential veiling entre as SADs de biomassa e número de indivíduos podem variar dependendo da escolha do modelo e do conjunto de dados avaliados. No entanto, se a causa do differential veiling entre as SADs de biomassa e número de indivíduos for principalmente devido ao efeito de escala, uma explicação alternativa é que a escala do presente estudo teria que ser ampliada para podermos demonstrá-lo. Considerando então, os efeitos de amostragem apontados pelos nossos resultados sobre a medida de diversidade, destacamos que, apesar da importância do assunto, há uma escassez de estudos que investiguem o uso da biomassa como medida de abundância nas SADs, cujas implicações de diferentes efeitos sobre esta medida destacam a necessidade de estudos adicionais que possibilitem isolar o efeito de escala do efeito de tamanho amostral / The species abundance distributions (SADs) are considered an informative way to describe the biological diversity revealling one of the most wellestablished patterns in ecology: the predominance of rare species in biological communities. The generality of such pattern made it relevant to the analysis of other biodiversity parameters an to induce the development of theoretical models of SAD. On the other hand statistical models of SAD occupied a central role in biology as an empirical principle that underlies many ecological theories. Preston suggested in 1948 that SADs follow an approximately lognormal distribution, but that may appear truncated by the effect of sample size, being completely revealed only in large samples. This idea is associated with the statistical property of consistency, which implies that the accumulation of evidence - represented by the increase in sample size - approaches the samples distribution to the true model, as well as the estimates of the parameters to their real values. Beyond the effect of sample size, the SADs may differ depending on the measure of abundance adopted. Studies suggest that biomass could be a more efficient measure of abundance to reveal the underlying distribution of biological communities in smaller samples or scales (differential veiling). In this context, our aim in this study was to investigate and discuss the advantage of considering biomass in theoretical models of SAD. Thus we evaluated the effect of sample size on the quality of models fitness under two different measures of species abundance: biomass and number of individuals. We simulated samples of different sizes taken from an empirical database of Scarabaeinae beetles - recognized as a potential and relevant indicator in ecological studies. Further we adjusted the simulated samples to different SAD models and evaluated the efficiency of each kind of abundance index to reveal the correct model, as well as the accuracy and precision of the parameters estimates. Our results show that the efficiency of biomass to reveal the underlying distribution is not as general as suggested by previous works. According to our analysis criteria, biomass was not consistently as far more efficient in revealing the correct model or in providing greater accuracy and precision in parameters estimates than the number of individuals. Thus, the statement that the SAD biomass is not veiled on small scales or samples does not seem to be general. Moreover our results also indicate that the effect of differential veiling on SADs using biomass and number of individuals depends on the choice of the evaluated model and data set. However, if the cause of the differential veiling - between the biomass and number of individuals SADs - is mainly due to scale effects. An alternative explanation is that the scale of this study was not wide enough to show it. Considering the sampling effects studied here in biodiversity evaluation we highlight the lack of studies investigating the use of biomass as a measure of abundance in SADs which the implications of different effects on this measure indicate the urgent call by further studies on this subject, enablying us to isolate the effect of scale from the sample size